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工程用球铁,按其断裂类型大多属脆性断裂,因此用于处理脆性断裂的线弹性断裂力学,其相应指标K_(IC)也应适用于处理球铁断裂问题。通常均采用ASTM-E399作为测试球铁断裂韧性的标准,但在实际工作中却出现一些意外情况。现根据我们近年来的工作对其中两个问题进行初步的讨论。一试样裂纹顶端锐度对测量结果的影响按ASTM-E399标准,K_(IC)试样均需预制疲劳裂纹。文献[1][2]曾提出,鉴于球铁是脆性较大的材料,根据由[1]导出的G_c与裂纹锐度ρ的关系式: G_c(ρ)=G_c(O)+π/4ρσ_Fε_F式中G_C(ρ),G_c(0)分别表示裂纹顶端曲率半径为ρ和
The ductile iron used in engineering is mostly brittle fracture according to the type of fracture. Therefore, for the linear elastic fracture mechanics of brittle fracture, the corresponding index K_ (IC) should also be suitable for the treatment of ductile iron fracture. ASTM-E399 is usually used as a standard to test the ductile fracture toughness of ductile iron. However, some unexpected accidents occur in practical work. Based on our work in recent years, we have tentatively discussed two of these issues. The influence of the sharpness of a crack tip on the measurement results According to the standard of ASTM-E399, K_ (IC) specimens are required to prefabricate fatigue cracks. According to [1] [2], it has been proposed that in view of the brittleness of ductile iron, according to the relation between Gc and crack sharpness ρ derived from [1]: G_c ρ = G_c O + π / 4ρσ_Fε_F Where G_C (ρ), G_c (0), respectively, that crack tip radius of curvature ρ and